1. Field of the Invention
The present invention generally relates to a filter press arranged to separate a raw liquid to be processed into a filtrate of filtered liquid and residue through filtering or press filtering thereto. More particularly, a filter press is equipped with an improved detecting arrangement for detecting the position of filter cloths or filter cloth hanging rods in normal or abnormal condition of the filter cloths when operated to move downwardly and upwardly.
2. Description of the Prior Art
Conventionally, in a filter press filter cloth of the travelling type, a detecting arrangement as described above has been used to detect the abnormal condition of the filter cloths or filter cloths hanging rods. For instance, in Japanese Utility Model publication (second publication) No. 35,375/1982, there is shown a filter press of this type which comprises front and rear stands. A plurality of filter plates are arranged between the front and rear stands to be opened and closed or pressed. Filter cloths are arranged between each pair of adjacent filter plates suspended by means of corresponding hanging rods fixed to the upper edges of the filter cloths and moved upwardly and downwardly. A plurality of shutter members respectively are arranged above the corresponding hanging rods in an opened state and having detecting openings passing therethrough in the front and rear direction. A light emitting device is arranged on one of the front and rear stands. Another light receiving device is arranged on the other of the front and rear stands.
With the conventional filter press, when all of the hanging rods take the predetermined upper position the shutter members are raised to the high position with the detecting openings thereof defining a light path. Meanwhile, when some hanging rods fail to reach the predetermined upper position due to an accident, the corresponding shutter members stay in a position lower than the high position. Thus, the light emitted from the light emitting device is interrupted by said shutter members resulting in the light receiving device generating a signal representing an occurrence of an abnormal condition.
Meanwhile, in the conventional filter press shutter member is associated with a shutter plate which is accommodated in a corresponding guide box supported by a corresponding filter plate. The corresponding shutter member is slidably supported to move upwardly and downwardly and has apertures corresponding to apertures of the shutter plate to permit the light emitted from the light emitting device to pass therethrough.
The conventional construction as described above has the following disadvantages. First of all, since the guide boxes and the shutter plates are mounted on the corresponding filter plates which are operated to be opened and closed, (for instance even if some filter plates are slightly inclined) the light emitted from the light emitting device may be interrupted by the corresponding guide box and the shutter plate. Thus, the detection of the condition of the filter rods lacks sufficient reliability. Meanwhile, in the conventional construction, even when some filter plates fail to take a predetermined opened position due to an accident, the corresponding filter cloth, and hence the corresponding hanging rod following said filter plate may raise the corresponding shutter member to the high position. Accordingly, the light path can be held in a normal condition, that is to say, the emitted light can reach the light receiving device so that the abnormal condition of the filter plates can not be detected.
Furthermore, the prior art is over complicated in construction because each shutter plate is supported by each corresponding guide box which is mounted on each filter plate by means of support members.